Unsurprisingly, the stories from each side involved have some key differences.
Here's what the US says.
Two Russian Su-27 fighter planes were flying in tandem over the Black Sea just west of Crimea, where the American drone was flying.
Then, the Su-27s began to literally play around with the Reaper, continually flying right in front of it and dumping fuel on it. Eventually, this led to one of the Su-27s clipping the Reaper's propeller, causing it to crash land in the Black Sea. The Reaper was deemed to be a "complete loss."
Here's the official statement of the US.
American military officials said the unarmed Reaper drone was flying a typical reconnaissance mission when it was intercepted by two Russian Su-27 fighter jets about 75 miles southwest of Ukraine's Crimean Peninsula, which Russia has used as a base for launching devastating strikes.
"Several times before the collision, the Su-27s dumped fuel on and flew in front of the MQ-9 in a reckless, environmentally unsound and unprofessional manner," the military's European Command said in a statement. "This incident demonstrates a lack of competence in addition to being unsafe and unprofessional.